The Minamata Disaster and the Disease That Followed

Mercury poisoning that sickened an entire Japanese town

Mercury pact falls short on Minamata. Credit: / Google Images

It started with the town cats. In the mid-1950s, the people of Minamata, Japan began to notice their cats were going crazy and falling into the sea. Some people thought the cats were committing suicide.

Soon after, a strange illness appeared to be going around town. The people of Minamata reported numbness in their limbs and lips. Some had difficulty hearing or seeing. Others developed shaking (tremors) in their arms and legs, difficulty walking, and even brain damage.

And, like the cats, some people seemed to be going crazy, shouting uncontrollably. Something was affecting their nervous system.

Finally, in July 1959, researchers from Kumamoto University discovered the source of the illness –– high levels of mercury poisoning –– which they then named Minamata disease. But how were all of these people (and cats) being poisoned? 

The Minamata Disaster

Minamata is a small fishing town on the coast of the Shiranui Sea. Because of its location, townspeople eat a lot of fish. The fish-based diets of the people and cats of Minamata seemed to be the common thread between those showing symptoms, leading scientists to suspect the fish in Minamata Bay were being poisoned.

A large petrochemical plant in Minamata, run by Chisso Corporation, was suspected immediately. Chisso denied the allegations and continued its manufacturing without changing its method of production.

 Chisso continued to deny its involvement or that its mercury waste was causing any illness. (It was later discovered that Chisso Corporation had dumped an estimated 27 tons of mercury compounds into Minamata Bay.)

As the mercury dumping continued, poisoned women gave birth to poisoned babies. These children were born with severe deformities including gnarled limbs, mental retardation, deafness, and blindness.


The fishermen of Minamata began protesting Chisso Corporation in 1959. They demanded Chisso quit dumping toxic waste and compensate them for their illnesses. Chisso, in turn, tried to make deals with people affected by mercury poisoning using legal documents that stated it would compensate individuals for their illnesses, but would accept no present or future liability. Many people felt this was their only chance at receiving any compensation, and signed the papers.

Recovering From the Minimata Poisoning 

Chisso finally quit poisoning Minimata's waters in 1968. According to the Japanese government, 2,955 people contracted Minamata disease and 1,784 people have since died. Researchers believe, however, that the criteria the government uses to diagnose Minamata disease is too strict, and that anyone showing any level of sensory impairment should be considered a victim. To date, Chisso has financially compensated over 10,000 people, and continues to be involved in suits regarding the matter.


In October 1982, 40 plaintiffs filed suit against the Japanese government, saying it had failed to stop Chisso from polluting the environment and had actually looked the other way while Chisso violated pollution laws. In April 2001, the Osaka High Court determined that the government's Health and Welfare Ministry should have begun taking regulatory action to stop the poisoning at the end of 1959, after researchers concluded that Minamata disease was caused by mercury poisoning. The court also ordered Chisso to pay $2.18 million in damages to the plaintiffs.

On October 16, 2004, the Supreme Court of Japan ordered the government to pay 71.5 million yen ($703,000) in damages to the Minamata disease victims. The Environment Minister bowed in apology to the plaintiffs. After 22 years, the plaintiffs achieved their goal of making those responsible for Japan's worst case of industrial pollution pay for their negligence. In 2010, Chisso was ordered to pay 2.1 million yen and monthly medical allowances to those not originally certified by the government as having the condition. More than 50,000 people applied for this compensation, showing how, over five decades later, the effects of this disaster are still felt. 

Information for this article was taken from:
- American University, The School of International Service. Minamata disaster.
- Kyodo News. Unrecognized Minamata disease patients to sue government. Japan Today, October 17, 2004.
- Mizoguchi, K. Court orders damages paid to Japan poisoning victims. The Boston Globe, October 16, 2004.
- Olson, D. A. (2002). Mercury. eMedicine.
- Tanaka, F. Negligence clear in Minamata case. The Daily Yomiuri, October 17, 2004.
- The Japan Times. Mercury pact falls short on Minamata (2012)

Continue Reading